Sounds like exactly what Jayce needs. After you spend W buff, go to malee form, QWE then benefit from youumu's active. Just wondering, would greater attack speed from items such as Youumu's make attack animation of hammer form's Q and E faster or is it only for autoattacks? Because it seems to me that canon's W does indeed make attack animation of his abilities faster, not only autoattacking.

Cleaver is suboptimal on Jayce for the same reason trinity force is : his skill rotation has 0 synergy with it.

There is no situation where you are applying cleaver stacks on a target and then doing your damage unless you are some pure fat bruiser Jayce.

Whoever down voted me (I'm suspecting Warrrax here) clearly can press the buttons and land some skills but has no idea how to make optimal use of Jayce and his skillset - instead wishing to force a cookie cutter AD caster build on him without thinking about how it actually affects him.

I don't downvote people who bring new ideas to the table and debate them in a reasonable manner.

But anyways, even if you put the cleavers %pen aside for a moment, BC still has significantly more AD and gives you health. As a first item, AD/health is more important than crit. Crit is a multipler and works great lategame but only with 1 skill, hypercharge and your occasional autoattack.
After BC I get another brutalizer and eventually upgrade to Ghostblade.

But seriously? "No situation?" Most of the time after qballing, dont you autoattack/hypercharge? That gives 4 attacks immediately which works with your Ranged Ult 10-25% armor reducer AND gives 4 black cleaver hits. (or you use hyper then gapclose and auto in melee).

Since people are being uncool and taking quote out of context, the long version of why Ghostblade is only so-so early on and midgame:

Jayce tends to autoattack using his HyperCharge which has a low CD, resets autoattacks and thus allows a 4.9 AD ratio in 1 second of shooting which is very impressive. Attack Speed is totally irrelevant during this action and the Hypercharge CD is pretty low and the attack is at range (unless you pop it, then gapclose and triple melee before knockback).
Therefore this is why I belive Ghostblade Clickey is underused on Jayce. You will many times Qball, Autoattack/Hypercharge, then immediately goto Melee form with gapcloser, knockback. You might get in a few autoattacks during this time but within 4 seconds you can also pop back to Range and use another hypercharge and non-gated-Qball which is WAY better than staying in melee form, right?

I suppose after your hypercharge, gapclose, knockback into wall, you could pop Ghostblade and speed up your autoattacks and chase ability. But you DID just slow them and bash them into a wall, and you can pop back out as I said and do another Qball,ranged autoattack/hypercharge. You arent 'helpless' like a typical melee after they escape from your gapcloser.

But anyways, even if you put the cleavers %pen aside for a moment, BC still has significantly more AD and gives you health. As a first item, AD/health is more important than crit. Crit is a multipler and works great lategame but only with 1 skill, hypercharge and your occasional autoattack.

Really, you shouldn't be rushing Cleaver nor Ghostblade unless it's a very odd, specialized case. It's not Cleaver vs Ghostblade as first item, it's Cleaver vs Ghostblade after you get some other AD like a LW/BFSword(or even IE).

Cleaver only gives you 20 more AD than Ghostlade. By the time you are upgrading your brutalizer, that's not as valuable as improving the chances of your W critting or the utility of the active.

And ultimately, Jayce while Jayce is an AD caster early, he is first and foremost an AD carry with massive front loaded burst late game. That means auto attacking multiplication is still king, and because you optimize to kill them with your first W, you really want that part to be hitting harder. Especially against other glass cannon champions. Consider that Jayce already has a built in 25% shred late game against the target he is about to Hypercharge. Against things that threaten you "with death unless they die in the first W," you are already probably doing true damage. Not to mention, in those cases? The IAS from the active will give you more DPS post W than the Cleaver Shred will. Especially if the Ghostblade crit chance nabs you another crit.

To Warrax, the point that seems wrong to me is that you would press W, go to hammer gap closer, than tripple attack in melee form. There seems to be great confusion as to what W applies to. It says it buffs next 3 attacks, not only autoattacks. So if you spent your first of three buffed attacks for hammer's Q (gapcloser), you wouldn't have buffed next 3 autoattacks in melee form but 2. You can actually spend all 3 buffs of W for abilites, cannon's Q, hammer's Q and hammer's E. Although you don't benefit from autoattack reset function of W in that case.

And yes, we seem to agree about enthropy at least

But new food for thought: Lightbringer as you know is anti Teemo and Akali and item, but its passive: Unique - Vanquish: Basic attacks have a 20% chance to deal 100 bonus magic damage. (So, if you autoattack-3 W's- autoattack), you sure get that 100 bonus damage. Effect doubled for non-champions I feel this effect more than I ever did BC or LW (although 20% chance of it doesn't sound like much), you can really feel that. So it seems to me it might be good stuff to buy even when there are no invisible jerks in the enemy team. It's also very cost efficient.